


Parallel Fifths

by crowind



Category: BanG Dream! Girl's Band Party! (Video Game)
Genre: Gen, and rui as sir not appearing in this story
Language: English
Status: Completed
Published: 2020-10-15
Updated: 2020-10-15
Packaged: 2021-03-09 02:59:37
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,639
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27027715
Author URL: https://archiveofourown.org/users/crowind/pseuds/crowind
Summary: Once is a coincidence, and twice is a bad habit in the making. But when Sayo once again finds Touko sighing heavily to herself, she finally accepts that having -sensei attached to her name is pretty nice, actually.
Relationships: Hikawa Sayo & Imai Lisa, Hikawa Sayo & Kirigaya Touko
Comments: 12
Kudos: 45





	Parallel Fifths

**Author's Note:**

  * For [la_comtesse](https://archiveofourown.org/users/la_comtesse/gifts).



> A very belated birthday present for la_comtesse. Happy birthday, kuro!
> 
> This fic follows up on the recent JP event where Touko somehow manages to recruit Sayo, Kaoru, Tae, and Misaki to give her a crash course. Hopefully it's still readable without having read that event, or even knowing who Rui or Touko is.

It was a familiar scene. Sayo was sitting alone in the family restaurant trying to enjoy the new flavor of the season in peace — chocolate pizza fries, guaranteed to not outlast fall. A hyper-fashionable teenage girl also sat alone on the next table over, sighing deeply to herself as if the world was ending tomorrow. Once was a coincidence, but twice was a bad habit in the making. 

Holding off a long-suffering sigh of her own, Sayo asked, "How can I help you, Kirigaya-san?" 

Touko clasped her hands together and regarded Sayo as though she was made of diamond. "Sayo-sensei! You're always there for me!" 

As again the problem seemed to be Touko's guitar, once Sayo finished her fries they adjourned to CiRCLE. Roselia had no rehearsal today as they — by which Sayo meant Yukina, specifically — had been haunted by disappointing mock exam results. Sayo had been planning on private session in the studio regardless, but she'd been planning to savor her lunch a little longer. Alas, sacrifices must be made, she told herself. 

Sayo cleared her throat, catching Touko's attention. For someone supposedly mired in crisis she hadn't once put down her phone since entering CiRCLE. 

"I was under the impression this was an emergency." Although Touko's definition of emergency seemed lenient. 

"It is, it literally is! But not like, literally." Finally, under Sayo's reproachful stare, she stowed her phone. Cracked her knuckles, then her neck, and finally, finally took her guitar out. "Now there's the signature Sayo-sensei look. Okay, I'm ready!" 

Touko rambled, "So just so you know, I've been practicing hard since last time. I tried keeping up with all the things you taught me, and like, there's your voice in my head scolding me when I slack off, so I'm sure I've gotten better. Thing is, Rui still has nothing to say. Like, literally nothing, no criticism, no praise." 

She seemed miffed, as if Rui's silence was a greater insult than anything she could have said. If Sayo remembered right, Rui's name had come up the last time Touko had needed a crash course, too. Sayo wracked her memories for Rui's last name. "Correct me if I'm wrong, but it seems that this… Yashio-san… is the main composer of your band?" 

"Yeah! Rui composes, then Nanami arranges for the whole band and Shiro — that's Mashiro — writes the lyrics. I mean, we all get a say on how the music's going to sound but Rui's standards are sky high so we usually go with hers in the end." 

In other words, as Yukina was to Roselia, except less all-encompassing. Sayo shook off her imagination before she started type-casting the rest of Morfonica into Roselia's mould, especially the _gyaru_ before her. She was beginning to see Touko's problem, but just in case, she prodded, so Touko continued, "This time I'm going on the offensive, be proactive, be the change, et cetera. Rui's never gonna see this coming. I'm gonna to make her admit I'm good and give me better parts." 

"And how do you plan to do that?" 

"By writing my own song, of course! Except…" Touko smiled sheepishly. "I'm not sure where to begin. Or end. Or just how this thing works. And don't think I didn't see your super skeptical face just now, Sayo-sensei! You're just like Rui. And here I thought I was your favorite student." 

"I never agreed to taking you as a student permanently." Nevertheless, her heart fluttered at the word 'student', and vacuous warmth filled her head until it felt too big for her neck. She, Hikawa Sayo, a teacher. The thought punctured her ego. Being a teacher came with responsibilities as serious as the student's future as a musician. Sayo would have to think of it in terms of what Touko needed more than what she, either Sayo or Touko, wanted. 

Carefully, she said, "You're still a beginner, Kirigaya-san. I wouldn't say it's too early for you to start writing a song, but without a proper grounding in the techniques I don't think you'd get very far. Especially because you, Kirigaya-san, by your own admission learn best by watching others. Last time I managed to teach you because there was guideline that I happened to know how to follow. A score, I meant a score, Kirigaya-san." 

Touko tilted her head like a confused puppy. "So doesn't that mean this time I just need to… write my own guideline and ask you how to follow it?" 

"I'd think you would have to internalize the guitar first before you could write anything satisfactory. And that does mean learning the fundamental theories and techniques, even though you might find boring, until they're available to you as if by reflex." 

"Boo. Can't we just jump straight to playing challenging songs? I'd be learning the scales or whatever and play something cool — Okay, okay, I get it, stop looking at me like that. I'll do it 'cuz I trust you, Sayo-sensei. Ah, but can we keep this a secret from Rui? I wanna see the look on her face when I show her up with a banger." 

And when Touko held that much fire in her eyes, who was Sayo to voice her doubts? 

* * *

A frivolous sense of fashion and an even more frivolous conduct and manner of speech. Among other people, regardless of how they related to her, an audacious force of nature. A penchant for flashy performance and a love for the spotlight that gave the stench of a gloryhound. In other words a natural lead guitarist in the way Sayo was not and couldn't relate to. Yet rather like another _gyaru_ Sayo knew, Touko took her role seriously and worked twice as hard to be the guitarist her band needed. This all Sayo knew firsthand; Otherwise she wouldn't have reached out a second time. 

Even so, she couldn't help but harbor a doubt, two in fact, one more reasonable than the other. 

An upside down rabbit dangled in and out of the corner of her sight, winking and smiling cheekily, not unlike its owner. Sayo put her pencil down. "Weren't you with Minato-san?" 

"We're not a buy one get one deal, you know." Without asking, Lisa sat herself opposite Sayo. They were sitting on the cafe outside of CiRCLE. It was a fairly breezy afternoon in fall, and not for the first time nor the last time Sayo wondered if Lisa's shoulders weren't cold. The chillier the weather, the lower her cut. Her lips were pinched at the mention of Yukina, and in a blink stretched from end to end. The full force of her bright persona hit Sayo as she said, "I didn't want to disturb you since you seemed so serious. Well, more serious than usual. Is that for our next song? Looks, uh, methodical." 

Sayo felt a stab of guilt. It was the first time in the week that Roselia had a band rehearsal, and Sayo was using break time for a different band's benefit. But no, she told herself, through teaching she was also learning, and anything Sayo learned would be useful for Roselia. Lisa wouldn't judge her for that. 

Sometimes Sayo could almost believe Lisa wouldn't judge her for anything. She unclenched her fists, careful not to wrinkle her handiwork, and summarized her encounters with Touko. Ending with, "And why are _you_ so happy about it," when Lisa's smile had grown unbearably ticklish. 

"'Cuz, look at you really getting into it, even going so far as writing an etude." Lisa exaggerated a double take. "Or ten. Not bad, Sayo-sensei." 

Sayo shrugged to shake off the heat in her ears. It was a different sort of warmth that filled her chest to the point of bursting, and she needed to put it out with a dose of reality. "Most of them are duds. And I could do no less with how enthusiastic Kirigaya-san approaches the guitar. She's pre-disposed to retaining crippling gaps in her techniques unless someone forces her to practice properly." 

"And that someone is you. I see, I see." Lisa nodded to herself, still grinning. Then delicately, "Though I can almost see the question mark above your head." 

Sayo definitely did not run a hand through her hair because she took Lisa's words literally. Lisa in all her nosiness had given her an easy out. But talking to Lisa about her worries, as petty as they were, had also become easy. "I'm not quite sure I am the right person for the job. The last time Kirigaya-san only succeeded thanks to Seta-san's interference. In fact, I do believe Seta-san deserves most of the credit. Her style is more suitable to Kirigaya-san. Whereas with my method, I'm not sure if it wouldn't be a waste of her time, or even harmful to her development as a guitarist." 

Of course, Sayo harbored these doubts at the same time she was revising these etudes and planning to send them to Touko in the evening. Lisa's thoughtful gaze said she was thinking of the same. But instead of pointing it out, she said, "Well, you know Touko better than I do. But look at it this way. She came to you again after tasting your bootcamp, so Touko must've decided she did learn a lot from you. Why not see how it'll go this time? Besides, you were always going on about there being no shortcut to being good at music. I can vouch that having a good foundation is important, too. Gotta know all the rules before you can break it, right? And you're definitely the person for the job on that part, not Kaoru." 

Despite her appearances, Sayo knew that Lisa fell more on the methodical side, probably due to Yukina's influence. So her support wasn't unexpected, but it still heartened her. But thinking of Yukina's influence, and the reason Lisa joined Roselia at first, her other concern floated to the surface. 

"There's another conundrum. Kirigaya-san's purpose is… Imai-san, how well do you know Yashio-san?" 

"Yashio… Rui, right? That girl who feels like someone put you, Yukina, and Rinko in a blender? Can't say I do." 

Before Sayo could object to that characterization, she sensed more than heard an overwhelming pressure approach, and unconsciously moved her body to cover her music sheets. It was Yukina, and a slight displeasure marred her usually calm expression. "There you are," said Yukina curtly. "How long are you going to spend dallying around?" 

Lisa's mouth opened, but Sayo beat her to it. "The break we agreed to should last another five minutes," she said pointedly. "And I saw Udagawa-san and Shirokane-san leaving the premises. No doubt they will return by the end of five minutes, but not before then." 

Yukina grimaced. Then she shrugged, a lazy twitch of just one of the muscles on her right shoulder. "I suppose it can't be helped. Don't be late, you two," she threw over her shoulders. 

"Actually, Yukina, I wanna talk to you…" Lisa was already getting up and jogging. Unless Sayo's eyes were playing tricks, Yukina actually quickened her pace and turned her head so she wouldn't even catch Lisa in the corner of her vision. Sayo was left contemplating an old adage, if it was possible that the things that were changing were also the things that stayed the same. Then she wrapped her cardigan tighter around herself, tidied up her things, and walked back toward the studio, using the brief time left to shift her mind toward Roselia once more. 

* * *

As she'd told Lisa, only a handful of the etudes survived Sayo's revisions and her subsequent attempt at playing them herself. What kind of a teacher would she be if she couldn't master her own exercises? That took the better part of the evening, so it was only the next day, a Sunday, that Sayo managed to send them to Touko. Ideally it would've been in person, so she could get Touko to start on the right foot forward, but Morfonica had a band rehearsal today and Roselia did not, and Sayo needed to catch up on her own progress. 

Talking to Touko over the phone was almost as good as face to face, without the distraction of her ever-changing expression. Though that came through in the tone of her voice anyway. _"Whoa, I'd predicted you'd send me one killer practice piece, but five, and all to be done in a week? Sayo-sensei, you're going to kill me!"_

Sayo massaged her temple. "And I'd thought you were past complaining, but if that's how — " 

_"Nonono, I take it back, I'm not complaining! I just don't know how I'm going to fit all of these with the new score Rui's brought out, and she's been threatening to downgrade my part — but I'm not complaining! Can't wait to see Rui's face when I finally show her who's the boss."_

Rui again. It was all a coincidence, she told herself, her mind seeing a pattern where there was not. Although there was an enthusiastic but unskilled _gyaru_ trying her hardest to make an aloof but skilled musician turn her head, surely the two ran along different lines. And even if they were similar, what of it? Would she meddle in the business of near strangers, and why? Yet Sayo still felt as though she should say something — at the very least in order to satisfy her curiosity — as much as she shouldn't, and in her hesitation Touko seemed to have lost interest in her call. _"So anyway, I gotta go now. I'll see you in a week, Sensei! Thank you so much again, you're a lifesaver, you know that?"_

Sayo had the entire flat to herself today. PasuPare had the day off, therefore Hina tagged into a study session with Chisato, Aya, and Maya that she definitely didn't need. Her parents had a rare weekend where both were free and used it to spend the entire day outside the house. Sayo couldn't understand her family sometimes. But it did leave her with hours of blissful solitude to practice in. 

In any case, Sayo had nothing to do but to polish her own skills. Not one hour into it, and the door bell rang. Curious, Sayo answered through the intercom. "Yes?" 

_"Oh, hey, Sayo. I was in the area and, uh, I know you're busy — "_

"Not at all. Would you like to come up?" 

Sayo had expected Lisa to decline, probably because Lisa had sounded too bright, as if she'd expected Sayo to turn her away. But in the end she answered affirmatively, and Sayo punched the button that would allow her entry. Then she bolted into her room and changed into something more suitable for receiving guests. It wasn't Lisa's first time — and only Sayo's second in a lifetime — she wasn't normally so impulsive in inviting a friend into her house. But normally Lisa wouldn't be here either, not when she could've been helping Yukina write their next song. 

As Sayo was beginning to fear Lisa had been so out of it as to forget her unit's number, she came knocking at the door. Lisa slipped inside, smiling like she was caught coming back outside of curfew. "Heya. I was just in the area and thought to, uh, drop by. Not, like, as an afterthought, I mean, you're not — this is a bad idea." 

"Why? I asked you to come in," Sayo said earnestly. And what was wrong with being an afterthought when it was obvious from Lisa's attire? Today was definitely too cold to not wear a jacket, and Lisa only had a flimsy T-shirt covering her shivering shoulders. Her magic purse covering for all exigencies was missing. There was no way she'd planned to walk all the way to Sayo's home, or anywhere farther than her neighbor's house. And just like that, the pieces fell into place. "Especially if it's related to Minato-san — Ah, I haven't talked to her today, but she'd declined my invitation to practice together today, saying she'd wanted to focus on finishing the song. And you'd only come to me like this if there was trouble with her." 

In hindsight, Sayo wondered what idiotic notion made her believe spouting her deduction could have helped. Lisa stared with something like fear. And guilt, so much guilt as she sputtered through several false starts. "That's not… I mean if that's how I've been treating you, I'm sorry! But you're not just a rebound friend, Sayo!" 

Sayo didn't understand either that phrase or what exactly was making Lisa upset. Though she hadn't denied having just come out of a trouble with Yukina, so Sayo thought that must've been the bulk of it. Thinking fast, she encircled her fingers around Lisa's wrist without touching. Lisa looked up at her with bewilderment, but she didn't move. Sayo said, "I didn't mean to imply I am entitled to more than what you've given me. Even you can't hold the same affection for all your friends, and it's entirely natural you would treasure Minato-san the most. I don't mind, so please, would you sit down? And have some tea. I'm quite sure we still have some of the cake Hina'd received from Hazawa-san, so please have it as well." 

Her bribe seemed to have worked, somewhat. Lisa made a great effort to wipe the despondency off her face. Sayo left her to it, escaping to the kitchen to retrieve the things she said she would. When she came back Lisa seemed more like her normal self. She still tried to apologize, so Sayo pushed the tea and cake on her and steered the conversation to something more productive. For example, untangling what exactly had happened and if it would jeopardize Roselia, though she didn't say it in so many words. 

Inhaling tea fumes, Lisa finally said, "I wish I hadn't pushed her so hard. Yukina's last mock exam result was kinda scary, so — I don't know if she told you this, but her parents were suddenly concerned and I guess they had A Talk. And I guess she'd changed because she didn't just forget about uni and focus on Roselia. Anyway, I thought I should take at least one burden off her shoulders." 

That much Sayo had known. Since the FWF, Roselia had been taking it slow. Partly so as to make the best decision towards becoming a pro band, and partly because four out of five members had university entrance exams to contend with in the near future, some better than others. "Therefore you took it upon yourself to write the next song so Minato-san could focus on her studies for the time being. I might have heard." 

Sayo wondered how much of Lisa's draft had survived until now. Lisa having creative differences with Yukina was progress, she supposed, however Lisa herself thought of it. The manner in which those differences were resolved, not so much. 

"I gave it to her last week. She usually turns out revisions much faster than this, so I started wondering if I'd bungled it so terribly it was unsalvageable." Lisa took a sip of the tea before continuing. "So today I went over to her room and asked if I could redo it. It was a long shot, anyway, if she'd thought the first attempt was so bad why would she give me another chance? So I told her this time I'd get, um, your help, but that kind of got her angry instead." 

Sayo blinked at the unexpected cameo. Quickly, Lisa said, "So then I started pushing about that too, and I guess things kind of spiralled out a bit and… I said things I shouldn't, knowing it'd piss her off." 

Sayo touched her shoulder in an awkward mockery of a comfort, and Lisa let out a laughter muffled by her hands. "Thanks, Sayo, but it's really my fault. I got _one_ song down and let it get to my head, and now I'm giving Yukina extra trouble she wouldn't have if I hadn't tried. I told her that, and then she…" Lisa shrugged. "Anyway, here I am now." 

Even now she was still eliding Yukina's behavior to preserve the dignity Yukina herself didn't care much about. But it was enlightening, Sayo supposed. She urged Lisa to eat the cake, buying time to think. 

"I don't know what Minato-san said to you, but I think I understand her anger. I would feel the same if you'd told me you regretted trying to improve your songwriting, and with such an irresponsible excuse as consideration for Minato-san." 

"I-Irresponsible?" 

"It could sound as if you were giving up on improving yourself, or worse, that you thought Minato-san wanted mindless drones in her band when that couldn't be further from the truth. A misunderstanding of Minato-san's character and a betrayal of her trust in you, in one hit." 

Sayo was exaggerating a bit, probably a bit too blunt in expousing the worst faith reading of the situation. Lisa looked like she'd found a cockroach in her cake. Suddenly her lips curved in her patented obnoxious smile, the one aimed at herself and inviting the other person to also laugh at her. "Are we talking about you, or Yukina? Well, Yukina did say you'd be furious if you'd heard." 

"Minato-san did?" Now it was Sayo's turn to feel uncomfortable, remembering the incident Lisa alluded to. That other time Lisa had disparaged her own skills, and Sayo had poured her fury on her. On one hand Sayo had genuinely felt betrayed, and not a little hurt that Lisa would easily disparage herself, and then so easily forgive Sayo. On the other hand it still wasn't one of her greatest moments. 

"Ah, don't worry, I've never told her about that other time. But you know, the fact that there was another time, and then I did the same thing to Yukina. No wonder she was so wroth…" 

"It might not be for the same reason. We're different people after all, Minato-san and I, with different relationships to you." 

"Different relationships, huh. Sometimes you're so dense I forgot… No, never mind." Lisa trailed off, opting to play with the half-eaten cake. How she could be so good at offering comfort and so terrible at requesting it, Sayo would never know. 

Sighing, she ignored the backhanded compliment and said, "Consider that this is a highly stressful period for us third-year students. And if I may hazard a guess, it doesn't seem as if you, Imai-san, are accustomed to having a quarrel, especially with Minato-san." 

"I mean, that's true, but, what, and you're used to fighting with Hina? … Sorry, that was stupid." 

Sayo allowed herself a dry smile. "Compared to you, I am an expert. And I'm not saying that all little sisters are alike, but have a little faith that your bond is strong enough to withstand a little quarrel or two." 

Slowly, Lisa's frown eased. "Now that I've talked to you it's really quite petty, isn't it. I'm kind of embarrassed, but thank you, Sayo." 

"But I'm not quite finished yet. As long as we're reminiscing for the past, do you remember when I told you that you must not always mediate for Minato-san, for her own good?" 

"I remember, but how's it related?" 

"It also means that you should also acknowledge it when Minato-san hurts you." 

Lisa's stare wasn't quite unbearable — yet Sayo's gaze faltered down to her lips. Bad move, they were flattened down to sardonic line. "You think it's something I still need to learn." 

"Am I wrong?" 

Lisa sighed, averting her gaze. "That's not really the problem, is it? What good is that going to do?" 

It was as gentle a rejection as Sayo would ever get. The message was clear, _please trust me_. And Sayo had no choice but to do so, if only because she also trusted Yukina. 

Lisa clapped her hands. Discussion over. "Anyway, I've got it now, so thank you, Sayo, really. And now we, uh, what were you doing before? Guitar, like the dependable person you are? And what about after, do you maybe want to go somewhere?" 

"What else? Of course I'd intended to practice the entire day." _Not just a rebound friend, she said._ Well, Sayo meant to make good on that claim. "But if you'd care to retrieve your bass and join me, I'm sure we can come to an arrangement that would please everyone." 

"An arrangement…" Lisa rolled her eyes, belied by the giggle fluttering in her throat. "Deal, but tea break's on me, okay? Don't look at me like that, we're definitely having a tea break in the afternoon. You'll love it, I swear." 

Well, what else could Sayo have done? "If you insist, Imai-san." 

* * *

There were two kinds of guitarists. The rhythm guitarist, stalwart but often overlooked (although perhaps not as much as the bassist). Then there was the lead guitarist. Flashy gloryhound, and usually the first image associated with the electric guitar. Sayo was only a lead guitarist by technicality. Should Roselia acquire a second guitarist, she could easily see herself stick to the rhythm part that she was more comfortable with. 

Touko was strictly her opposite, a fact that became obvious in the first five seconds of watching her play. Sayo put flourishes into her performance only when she had the leeway, and quite honestly when she was too caught up in the music to deny herself. Touko seemed to shape her performance around as many flourishes and solo parts as she could cram into it. Which Sayo didn't have a problem with on principle as long as she didn't slack off on the actual sound. 

So far she seemed to have delivered on that promise. Gone were the flaws Sayo had pointed out during her first crash course — and a thousand more had arisen in their place, but it was to be expected. That was the essence of improvement. Touko was well on track to greatness, that was more than she could expect. Sayo'd had her doubts, but as the session went on she started seeing where she could be useful to Touko. 

Touko finished with a grand sweep of her arm, letting the last note reverberate in the small studio they were renting. Flushed with excitement, she asked, "How was that, Sayo-sensei?" 

"Before we go on, there's something I need to ask you. Why do you want to write a song _now_?" 

Touko's arm flopped to her side. "That again? I just wanna show Rui up. Not like, because I hate her or anything, I just wanna see her show something else other than her usual face, you know?" 

"I… don't know Yashio-san at all, actually." 

"Ahaha, Sayo-sensei, you're always so serious! Well, Rui's a bit like that too, actually, except she's even harder to crack. But you know it's there, deep inside, probably, a live, beating human heart. I mean, she seems like a robot and her standard's as unforgiving as a robot, but there's no way she'd have picked up the violin again and joined Morfonica if she hadn't followed her heart. So in a way I don't wanna make her regret that decision, you know? Gotta show her that it's worth it, that we — that _I'm_ not just wasting her time." 

"But don't tell her I told you all of that!" Touko added quickly, and Sayo promised she wouldn't. She didn't think she needed to, in this case. It might've been laziness, or indifference, but she had a feeling she could trust Touko's intuition. 

Plus there was no whiff of a thorny history chaining Rui and Touko together. 

Sayo nodded. "Then let's start from the beginning. We'll go through each note and you will do exactly as I say." 

Touko's groans would echo in the lessons to come, just another part of the unique ambience. 

**Author's Note:**

> I found the Sayo/Touko master/disciple relationship as the next step in Sayo's character development irresistible. The other stuff that made its way into this fic, eh, call it a fixation, or the only reason I still write in this fandom.


End file.
